Drying and roasting furnace



Sept. 15, 1931. 5. E. CONNOLLY DRYING AND ROASTING FURNACE Filed May 1. 1930 Z R w 7 O YE mm W MM 1 A 0 08 e G Patented Sept. 15, 1933 I OFF! GEORGE E. CONNOLLY, OF OAKLAND, CAL

COMPANY, OF NEW YORK, N. Y.,

IFORNIA, ASSIGNOR TO NICHOLS COPPER A CORPORATION OF NEW YORK BRYING A'ND ROASTING FURNACE Application filed. May 1, 1930. Serial No. 448,829.

This invention relates to multiple hearth drying and roasting apparatus and methods of using the same.

The objects of the invention include the provision of drying and roasting apparatus and also methods of operatin such apparatus'which will be dependab e, relatively simple and efiicient under a variety of different conditions of operation and in which the treatment of various kinds and grades of material may be accurately controlled.

The invention consists in such novel features, arrangements and combinations of parts as may be shown and described in connection with the device herein disclosed by way of example only and as illustrative of a preferred embodiment, together with such novel methods and steps of processes as may be described herein.

The drawing comprises a vertical sectional view, partly broken away, through a drying furnace comprising one embodiment of the invention.

The features comprising this invention may be embodied in furnace constructions of the same general class as shown in the numerous patents to J. B. F. Herreshoff, as for example No. 976,175 of November 22, 1910, and may incorporate, if desired, vari- 0 ous improvements such as for example, the improved shaft and rabble arm construction shown in the patents to Dudley Baird No. 1,375,346 dated April 19, 1921-, and No. 1,669,- 925 dated May 15, 1928. V

A plurality of vertically spaced or superposed hearths is indicated and designated respectively by the numerals 1 to 7. These hearths may be surrounded and supported 40 in the conventional manner as by a cylindrical furnace wall 8. A rotatable and internally cooled central shaft 9 extends vertically up through the center of the furnace and is provided with rabble arms as at 10 and 11. In the embodiment shown, two oppositely directed rabble arms are provided to cooperate with each hearth area in the usual manner. Suitable rabble teeth as at 12 are provided along each of the rabble arms for advancing the material being treated successively over each hearth down through the furnace.

While in the drawing, eight hearths only are indicated for simplicity, it will be understood that various features of the invention are applicable alike to furnaces having a number of hearths in the neighborhood of twelve and even to furnaces having a substantially larger number of hearths.

The central shaft 9 as here illustrated, may be provided with an internal conduit as at 13, the rabble arms being also provided with inner conduits of any desired well known form communicating with the conduit 13, whereby cooling fluid such as air carried by the conduit 13 may be allowed to pass through the conduits of the various rabble arms, and thence back into an annular space 14 between the conduit 13 and the walls of the shaft 9. The cooling fluid for example may be introduced at 1.3 through the usual adjustable damper intake at the end of the conduit 13 at the bottom of the furnace and the same fluid or a portion thereof, after having circulated through the various rabble arms, may be discharged from the top of the shaft 9 as through an adjustable damper 15,

rabble arm and shaft air cooling arsuch a rangement being more fully described in the patent to Baird, No. 1,375,346 of April 19, 1921.

At various of the hearths the shaft 9 may be provided with hot air discharging outlets as at 16, for discharging into the furnace a portion of the cooling fluid after the same has become preheated by circulating through the cooling conduits of the shaft and rabble arms.

The features above referred to are described in further detail in the two abovementioned Baird patents.

Referring now more particularly to the features comprising the present invention, it will be noted that hearths 5, 6 and 7, as shown in the drawing, are constructed sub- 95 stantially in accordance with the corresponding hearths disclosed in the Baird patents, whereas the hearths 1 to 4, inclusive, are of a different construction which, according to this invention, render the furnace particular- 10G 1y adaptable for use in drying, roasting and treating sludge or watery mixtures. To this end, the hearths Nos. 1, 2 and 3,.for example, may be constructed in the shape of annular hollow bodies the top portions of which are covered bysuitable screening material as indicated. Also if. desired one or more of the hearths as shown at hearth 4, for example, may embody similar hollow or concaved members partly covered ,over with screening as at 17 and partly covered with an annular imperforate plate as at 18.

With this type of drying apparatus the sludge or slurry mixture which is to be treated, may be conducted into the furnace through an inlet opening as at 19, for discharging the mixture onto the screening of hearth No. 1. A considerable proportion of the fluid of the mixture will thereupon pass through the screening into the cavity of hearth 1 from which the fluid may be conducted away as by a conduit 20. The conduit 20 may be also similarly connected to the corresponding cavities of the succeeding hearths Nos. 2, 3 and 4 as shown.

The screen areas of the upper hearths may be formed of wire netting of a mesh depending upon the coarseness of the material being treated, or if desired, other screening means such as perforated steel plates or combinations of perforated plates and wire or fabric nettings, may be used.

As the rabbling teeth provided on the rotating rabbling arms advance the mixture over the screening of the several hearths, the fluid components of the mixture are gradually drained away into the cavities of the hearths and either discharged through the conduit 20 or conducted thereby to other apparatus for further treatment depending upon the nature of the fluids thus obtained.

The mixture under treatment is accordingly advanced down through the furnace over the successive hearths, sufficient hearth area in the form of screening material being provided to permit the desired proportion of the fluid to drain away from the mixture.

' a point in the furnace where the mixture under treatment becomes sufficiently dry so that no further filtering or screening is desirable, the screening areas may be replaced by imperforate areas as at 18, or by the standard fire brick roasting furnace hearths as hearths Nos. 5, 6 and 7 shown in the drawmg. i

The cavitiesor chambers within the upper hearths may all be brought into communication with a suction pump as at 21, conduits as at 22 and 23 serving to accomplish this purpose. The drier may be heated by the use of one or more burners as at 24 mounted so as to pro ect flames into one of the lower hearth areas. Products of combustion from. these burners, together with the preheated gases from the discharge openings or arms as at 16, are conducted over the various hearths up through the furnace and such gases are then drawn downwardly through the material under treatment and through the screening of the upper hearths, and thence out to the suction pump. This arrangement, therefore, provides a very efiicient method of utilizing fully the heat of these gases, since the gases are discharged from the furnace only after passing directly through the material under treatment.

It will be observed that the above described construction provides a combined filter or screening device, drier and roasting furnace. Such an arrangement makes rapidly dry and roast sludge mixtures with a high degree of economy, inasmuch as opportunity is given for a substantial proportion of the fluid of the mixture to drain away without requiring the application of sufficient heat to evaporatethe same. This draining operation may be conducted with a high degree of thoroughness since the material is thoroughly rabbled and disintegrated as it passes over the several hearths and is agitated by the rabble teeth. During the draining operation the temperature of the sludge is rapidly raised to a point where evaporation of the remaining moisture takes place very quickly from the lower hearths. Meanwhile the heat of the products of combustion as well as the heat absorbed by the cooling system, is economically used as above explained, since the gases as discharged from the furnace are passed through the mixture during this agitation on the upper hearths.

It will be understood that the apparatus embodying this invention may be used for the roasting, drying, reconditioning or revivification of a Wide variety of materials such as the various ores, fullers earth and diatomaceous materials, kieselguhr, etc.

Such details of construction of the furnace walls and hearths and rabbling structure as may not be hereinabove fully described, may conform in general to the construction heretofore used in roasting furnaces of this general type, and more particularly as disclosed in the above-mentioned patents.

While the invention has been described with respect to certain particular preferred examples which give satisfactory results, it will be understood by those skilled in the art, after understanding the invention, that various changes and modifications may be made it possible to without departing from the spirit and scope 1. Apparatus for treating sludge mixtures or the like comprising a plurality of superposed hearths substantially circular in out advancing the material over the several linev and surrounded by an enclosing wall, substantial portions of the areas of said hearths having interstices permitting the passage therethrough of the more liquid components of the mixtures being treated, means comprising drip pans suspended beneath each of said hearths between successive hearths for receiving such liquid, conduit means for conveying such liquid from said drip pans to the exterior of the device, and rabbling means rotatably mounted in respect to each hearth for stirring the mixture under treatment and gradually advancing the same over the surface of each hearth and from hearth to hearth successively, openings being provided for permitting the material to drop from hearth to hearth.

2. Apparatus for drying and separating sludge mixtures or the like comprising a plu rality of superposed hearth structures surrounded by an enclosing wall, means mounted in the space between each pair of hearths for rabbling the material under treatment over the several hearths successively, openings be ing provided for permitting the material to drop from hearth to hearth said rabbling means and hearths being rotatable with respect to each other about a verticalaxis, said hearth structures having a perforated surface upon which the material is supported and cavities being formed within said hearth structures respectively, such cavities communicating with said perforations and being adapted to receive and drain away the more fluid components of the mixture which pass through the perforations, and means communicating with said cavities for conducting to the exterior of the apparatus such fluid as passes through the perforations, whereby some liquid, gaseous or vaporized components of the mixture may be extracted at each succeeding hearth and the treatment at the next succeeding hearth may be independent of such components.

3. Apparatus for treating sludge mixtures or the like comprising a plurality of superposed hearths each having perforated drainmg areas and containing cavities communieating with theperforations for draining and conducting away such material as passes through the perforations of each hearth, said hearths being surrounded and supported by an enclosing wall, a rotatable vertical shaft extending through the middle of said hearths and rabbling means carried by said shaft for hearths successively, openings being provided through said hearths for permitting the material to drop from hearth to hearth, such openings being independent of the cavities withinthe hearths and non-connnunicative therewlth except through said perforations.

* pparatus for, treating sludge mixtures 4. A and the like comprising a plurality of spaced superposed screen-like surfaces, the effective areas of which are substantially circular in outline, stirring means for advancing the mixture across each'of said surfaces and from one surface to the next in succession, such stirring means including rabbling elements movable through circular paths relative to each of said surfaces and substantially concentrically therewith, means suspended beneath each of such surfaces and enclosing the undersides thereof for conducting away such material as passes therethrough, heating means within the apparatus, openings being formed through each of such surfaces whereby the material under treatment may fall from one surface to the next and more and more of the fluid components of the mixture may be extracted through each succeeding screen-like surface, and said openings also providing passageways for heated gases which may circulate through the apparatus over the several surfaces and may in part pass through such surfaces and be conducted away with the other material extracted therethrough.

5. Apparatus for treating sludge mixtures or the like comprising a plurality of superposed hearths each having perforated drain ing areas and containing cavities communicating with the perforations for draining and conducting away such material as passes through the perforations of each hearth, suction means for promoting the passage of fluid through said perforations from the mixture under treatment, a rotatable vertical shaft extending through the middle of-said hearths and rabbling means carried by said shaft for advancing the material over the several hearths successively, openings being provided through said hearths for permitting the material to drop from hearth to hearth, such openings being independent of the cavities within the hearths and non-communicative therewith except through said perforations.

In testimonywhereof I have signed my name to this specification.

GEORGE! E. CONNOLLY. 

